Variable gain amplifiers may amplify the radio signals to be transmitted or the received radio signals to the desired power level, and then transmit the received radio signals to the backend circuit for processing. Variable gain amplifiers may be used in a lot of fields, such as remote toys, consumer mobile communication electronic devices, base station, military fields or space fields.
Variable gain amplifiers are required to have enough gain variation range. When used in phase array transceivers, the ideal variable gain amplifiers may keep the constant phase variation in the gain variation range. However, when the gain is varied, the real variable gain amplifiers do not keep the constant phase variation, and thus needs additional control mechanism. By introducing additional control, the real variable gain amplifiers may keep the constant phase variation in the gain variation range. However, this will increase control complexity.